Ultrahigh frequency oscillator system



y 1937- K. POSTHUMUS 2,086,335

ULTRA'fiI'G'H FREQUENCY OSCILLATOR SYSTEM Fi-l'ed Aug. 25, 1934 wan 577a flab (6/4 76 j v i ll' I I IIIII I II IYNVENTOR KLAAS POST H U MUS ATTORNEY Patented July 6, 1937 umrssmres ULTRAHIGH FREQUENCY OSCILLATOR SYSTEM Klaas Posthumus, Eindhoven, Netherlands, assignor to Radio Corporation of America, a corporation of Delaware Application August 25,

1934, Serial No. 741,393

In the Netherlands September 6, 1933 Y 5 Claims.

This invention relates to an arrangement for producing high frequency and ultrahigh frequency electric oscillations and more particularly to a thermionic generator in which the circuit determining the frequency lies between two or more electrodes of a discharge tube. As an example of such a generator, we may mention a magnetron-oscillator comprising two or more anodes which are symmetrically arranged with respect to an incandescent cathode and in which an oscillatory circuit determining the frequency of the produced oscillations is provided between the anodes. Oscillations are produced in this circuit since a negative resistance is inserted be-- tween the electrodes. However, it is necessary, in this case, that the resistance of the circuit substantially corresponds to the negative resistance between the electrodes. In many cases it will be desirable, however, that the resistance of the circuit be accommodated to the internal resistance. More particularly, when the frequencydetermining circuit of a magnetron-oscillator is constituted by an antenna-dipole, accommodation will be necessary, since the resistance of such an antenna is low and the negative resistance of a magnetron-oscillator is high.

According to the invention, the desired accommodation is ensured by connecting the frequency determining circuit to the electrode terminals through conductors, having such a length that the electric distance between the electrodes and the oscillatory circuit amounts to one-quarter wave length of the oscillations to be produced.

Preferably, the frequency-determining circuit is connected to the conductors through condensers having such a size that the influence excited by the interelectrode capacity on the total external impedance is compensated.

The invention will be more clearly understood by reference to the accompanying drawing which represents only the parts required for a good understanding of the working of the arrangement.

In this drawing, 2 and Q denote a sectional View of the anodes of a magnetron oscillator. The cathode of this oscillator, which is perpendicular to the plane of the drawing, is denoted by K. A field winding 26 may be used for the generation of oscillations. The source of anodevoltage is connected to the anodes 2 and 4 over conductors 24, the length of each of which amounts to one-quarter wave length of the oscillations to be reproduced. That is to say, each of the conductors 24 together with a portion of the bridging conductor 25 to the midpoint thereof, has substantially a quarter wave length so that a nodal point is formed at the midpoint of the bridging conductor 25. The oscillation circuit of the generator is constituted by both parts of a dipole antenna 6. One arm of this antenna is connected through the condenser 16 and the conductors B and 20 to the electrode terminal 2. The other antenna arm is connected through the condenser l8 and conductors iii and 22 to the electrode terminal 4.

According to the invention, the conductors 8 and II] have such a size that, together with the electrode supply wires 20 and 22, they have a length of one-quarterwave length of the oscillations produced by the generator. They thus achieve the required accommodation or matching of the impedance of the oscillatory circuit; in the case under review the accommodation of the impedance of antenna 6 to the negative resistance between the electrodes 2 and 4. In fact,

it will be appreciated that if the impedance at the end of a line having a length of one-quarter wave length be 2, the impedance at the beginning of this line may be represented by where R is the wave resistance of the line. By using this realization, which is known per se for accommodating the output impedance of an oscillator to the internal resistance of this oscillator, an arrangement is obtained in which the influence of the interelectrode capacity, which lies 0 in parallel with the resistance between the electrodes, viz. the resistance In this case the admittance is In this case the total admittance between the electrodes 2 and 4 amounts to zggx y where a'y is the admittance of the interelectrode capacity. When the condensers l6 and I8 are now given such a size that the impedance between the electrodes 2 and 4 will be and the interelectrode capacity is compensated.

What is claimed is:

1. A thermionic generator for producing high frequency and ultra-high frequency oscillations comprising an electron discharge tube having a pair of anodes symmetrically disposed about a cathode, an oscillatory circuitincluding two arms of a dipole antenna system, means including a pair of parallel conductors, each in series with a capacitor, interconnecting each anode respectively with one of said antenna arms for producing an impedance match between the portions of said circuit that lie within and outside of said tube respectively, and means including a source of direct current potential and circuit connections in series therewith interposed between said cathode and said anodes for supplying said discharge tube with the required polarization of its electrodes.

2. A generator in accordance with claim 1 and having a conductive bridge-circuit included in the electrode polarization means, the electrical length of each half of said bridge-circuit being substantially equal to a quarter-wave length of the oscillations generated.

3. A generator in accordance with claim 1 and having said capacitors so disposed in circuit with said impedance matching means that the interelectrode capacity is efiectively compensated.

4. An electronic generator for producing high frequency and ultra-high frequency oscillations comprising an electron discharge tube having at least one pair of anodes symmetrically disposed about a cathode, an oscillatory circuit including two capacitors so dimensioned that the interelectrode capacity of the discharge tube is effectively compensated, two arms of a dipole antenna system each arm being coupled to said oscillatory circuit through one of said capacitors, respectively, and a pair of impedance matching conductors, each conductor extending between one of said anodes and one of said capacitors respectively and having an electrical length substantially equal to a quarter wave length of the waves generated, and means including a source of direct current potential and circuit connections in series therewith interposed between said cathode and the anode connectedterminals oi the discharge tube for supplying to said discharge tube the required polarization of its electrodes.

5. A generator in accordance with claim 4 and having a conductive bridge-circuit included in the electrode polarization means, the electrical length of said bridge-circuit being substantially equal to a half-wave length of the waves generated. 1

KLAAS POSTHUMUS. 

